Compensated seal



COMPENSATED SEAL Filed April 2l, 1959 2 Sheets-Sheet 1 32 .5 0 l 5;ff 1. am" h v u- (Mei rf LNV/E522 /v BY ,Wa/6W iwf/44610 i invent/- July5, 1960 c. l.. HAMM ETAL COMPENSATED SEAL 2 Sheets-Sheet 2 Filed April2l, 1959 INVENTOR. (MPF/V55 l. /MM

myC-@015W arraea/syv t 2,943,873 Patented JulyrS, ,i960

United States COMPENSATED SEAL Clarence Lockwood Hamm and WilliamWidlansky,

Marblehead, Mass., assignors to General Electric Company, a corporationof New York Filed Apr. 21, 19529, Ser. No. 807,790

7 Claims. (Cl. A286-11.11)

This invention relates to a seal for use on a shaft and, moreparticularly, to a seal having means compensating for centrifugal forcesdeveloped during rotation of theshaft at high speeds.

In certain types of machinery it is often desirable to employ two ormore concentrically-rotatable shafts or a shaft rotating within acylindrical housing. It also may be necessary to prevent shaftlubricating uids from progressing axially along the shaft past a certainpoint. Gne means of accomplishing oil stoppage, for example, is to usean annular seal adapted to fit tightly over the shaft. A seal of thistype may utilize a continuous sealing element constructed of a suitableoil resistant bearing material, the element being in slidable contactwith the inside wall of an outer shaft or a housing.

When such a seal is used in equipment designed to operate over a widerange of speeds, the extreme centrifugal forces developed at the highend of the operational range can cause rapid wear or even seizure of thesealing element. This is largely a result of frictional heating causedby the high radial loads and the high peripheral speeds. If the sealingelement is made undersize so as to provide just the right amount ofsealing at high speeds, then at low speeds the sealing pressures may betoo low to seal properly. Therefore, there is need for a seal whichoperates independently of speed, i.e., which is not adversely affectedby the thermal effect of high speeds on the sealing element or theadjacent parts. Ideally, such a seal should include means forcompensating for the centrifugal forces while, at the same time,supplying only the desired sealing pressures at all speeds. ln addition,when the equipment is not operating, the seal should be capable ofpreventing gradual oil seepage past the sealing element.

Accordingly, it is an object of this invention to provide a seal for usewith a shaft, the seal being centrifugally-compensated over a wide rangeof rotational speeds.

A further object is to provide a seal' for use with concentricallyrotatable shafts, or a shaft rotating within a `cylindrical housing, theseal being self-compensating when subjected to the large centrifugalforces occurring during high speed operation of the shaft, and alsoproviding the desired sealing pressures at all operating speeds andWhile the shaft is at rest.

Briey, in one embodiment of our invention, we provide acentrifugally-compensated shaft seal for use between concentric shafts,or within a cylindrical housing, the seal having a transversely-splitannular sealing element acted upon by a plurality of lever-armssupported by a seal frame in such a manner that as r.p.m. increases, ordecreases, the peripheral sealing pressure exerted by the sealingelement changes to compensate for the effect of centrifugal force on theelement.

While the specification concludes with claims specilically pointing outand Vdistinctly claiming the subject matter which we regard as ourinvention, it is believed that the invention will be better understoodfrom the following description taken in connection with panying drawingsin which:

Figure l is an elevation of the seal, partially in section and,

Figure 2 is a cross-section of the seal, partially broken away to showthe support lfor the lever-arms and,

Figure 3 is a pictorial view of one embodiment of the lever-arms and,

Figure 4 is a further embodiment of the seal including a double sealingelement and,

Figure 5 is an enlarged view of the stepped, transversely-extending cutin the annular sealing element.l

While our device is equally useful for operation within a cylindricalhousing, .the seal is shown being utilized between a pair ofconcentrically rotatable shafts.

Referring now to the individual drawings, Fig. l shows a pair of hollow,concentric shafts such as might be found, for example, in a typicalaxial-flow turbo-machine. The inner shaft, which could carry av powertake-off, wheel, is indicated at 10, and the outer shaft, which might beused to drive a compressor, is indicated at. 12.

With use of our novel seal some relieving means should be provided forlubricating oil moving axially of the turbo-machine. In the embodimentshown, the oil is directed through a plurality of holes 13 in a machinedcylinder or runner 14 affixed to the inner circumference of the outershaft. The runner is preferably .re-

the accomcessed at 14a to save weight and to facilitate cooling. i

The recessed portion communicates with a plurality of oil outlet holes15 in the wall of the outer shaft 12 for relieving the system. u

Securely aixed to the outer circumference of the inner shaft 16 is acylinder, indicated generally at 16, which serves as a base or frame forsupporting the operating portions of the seal. The forward and aft facesof the frame 15 contain circumferentially-extending notches or seats'1S-1S. Disposed between these two 'axiallyspaced seat portions of theframe is a central portion 22 which carries a rim portion 24. The rimportion, substantially larger in diameter than the other portions of theframe, contains a plurality of axially-extending holes 26, chamfered at28 and 29. These holes are adapted to receive lever-arms capable ofbeing centrifugally-acted as described below.

One embodiment of the lever-arms 'utilized to make the seallself-compensating is illustrated in Fig. 3. Shown therein is acylindrical Ipin 30 having an enlarged end portion 32 and anaxially-extending neck portion 34. Approximately midway of the neckportion is a raised portion 36, which may be semicircular inconfiguration, providing a fulcrnm for the lever-pin when it is insertedin one of the frame rim holes 26. Preferably the hole diameter is suchthat there is single-point contact between the hole wall and theperiphery of the fulcrum 35 in order to facilitate the pivotingmovement. WhereV thev fulcrum has the semicircular configuration of the'embodiment shown, the holes 26 may be slightly recessed to prevent anysignificant axial movement of the lever-pins after they are snapped inplace. At the end of the neck portion 34' is a second raised portion 38forming a bearing surface for engagement with the sealing elementdescribed below.

Obviously, any suitable type of lever-arm could be substituted for thelever-pins 30. For example, va bar' In our device actual sealing isaccomplished by use of plurality of apertures 41 adapted to receive thebearing surfaces; The apertures extend only part way through Vthe diskand are .constructed so that the portion of each apertureA immediatelylsurrounding the,` inserted beating surface is only'slightly` larger indiameter than the latter in order that very little pivoting motion isrequired by the-*levers to 4cause the surface to vengage the aperturewallr- VEach aperturerisenlarged at`42Y to permit the necessaryn'freedomofl movement of the. lever-pin Jneck VTo maintain theannular-.disk-40 in position on the Y central-portion,Z2 of the frameand ,to prevent the lever pins 3l) from slipping Yout ofthe holes 26,retaining means,

are provided.' Y The Yretaining meansishown in Fig. l consist of a pairof annularmetalY rings 44 and 46. The rings are adapted tot overtheredge portions 1'8--18 of Y the sealv frame and may be 'held' thereby'vrany suitable method, such asY a force fit..V

beyond the disk under non-operating conditions. AVIf the disk were notdesigned to be used at high'cpe'ratingV speeds, and if there were nothermal expansion and contraction during operation, this Vwould be allthat would be necessary. However, under high speed operating conditions,the pressure of the disk periphery on the' outer shaft tends toincrease, primarily .as a result ofthe large 4centrifugal forcesaccompanying such operation, and

also due to the expansion caused byfrictionalheating. Without some meansof compensating for this increase in pressure, the sealingelement wouldwear very'rapidly Y or even seize. By utilizing the centrifugal forcegenerated in the seal during high speed operation of the shaft, the sealcan be made self-compensating by reason of the lever-pin arrangementdescribed above.' In other words,

as the centrifugal force increases, the enlarged ends 32'of the pins 30will tend to move outwardly, since theplns are free to pivotY abouttheir fulcrums 36. fin turn j pivots the smallery pin endsinwardlytowardsthe/ shaft-"f axis. These latter ends contain the bearingsurfaces 38 rwhich, sincey they-will now be in contact with the wallsfofY the apertures 41', act to oppose the centrifugal force tendingtospread the'gaps 5i9'and/6`0 'and'increase the relative Y Ydisk diameter.Therefore, 'as/speed increases, the levers ljlnithefsealrconligurationshown'in the drawings, the' sealing VYaction requires use of; bothperipheral and ra- YV dially-ext'ending surfaces of the annular sealingdisk 40. The mating surfaces 47 and48 ofthe sealing disk and the Vendring 46, respectively, are machined to a closetolerance Ito provide aradially-extending sealing surface. This Vis necessary since the disk isannular and, butrfor the radialfsealing action, Yoil could passV throughthe center Yof the disk, at'49,rup along Ythe outer face 47 of thediskQpast the retaining ring46, and thence axially along the innershaft. To insure that this radial sealing action is continuous, aplurality of sockets 50;are provided `in Y theliradially-ext'ending faceof thenrimV 24l opposite the 'Y disk, preferably lbetween .eachfof theholes 26. Howover, the'exact number of sockets vis notY critical.Y TheseY Vsockets are adapted to Vreceive springs 52 which extend Ysufficientlyto contact the kdisk to force it into continuousabutment with the ringV46. s

-When utilized, the ,runner V14 forms an axiallyextending bearingsurface for the annular sealing disk periphery, indicatediat 54, forperipheral sealing action between the diskY and a machined surface 55 onthe runner.` Use of the runner is not absolutely essential, khowever,and any suitably machined bearing surface could be Y provided on .theinner circumference of the outer shaft for cooperation with the sealingelement.

As-previously stated, Van object of our invention is to provideacentrifugally-compensated shaft seal which will maintain the desiredsealing Vpressure at all-speeds and 'While the shaft is at rest. VToinsure sealing regardless-of speed, the annular sealing disk 40 shouldbe made slightly voversize in relation to the inside diameter of theouter shaft (or the runner.). The disk is then transverselysplit bymeans of a stepped out, indicated generally Vat 58; By. referring to theenlarged view of Fig. 5, it will be seen( that thetransversely-extending*portions 59 Vand 60 of thestepped Vcut formslight gaps so as-to enable ,'the'disk,V which isYV slightly resilient,to be compressed to t inside the shaft. The stepped configuration of thecut is designed to insure against oil leakage, i.e., the walls oftheYradially-extending portion `61 of the Ycut are in close,r frictionalcontact, as opposed to the kgappedrV transversely-extending portions.A

- 'It will be obvious from the above description that the 'Y slightlyresilient disk Vtii'vill' tend to retain its original diameter undercompression. Therefore, since the disk is slightly oversize it will abutthe runner-.with just enough Y residual pressure to prevent oil fromseeping through and sealing effect at all speeds, Thus, rapid wear oreven seizureY of ,the'sealV duejto'thermal expansion and highcentrifugal forces is successfully'avoided. Wherer the sealingV elementcomprisesja. diski made ofA carbon 'or a like material,iit may bedesirable; although it is lnot ab-` solutely` necessary, toV providesomemeans of vreinforcement, such as a Vthin metalbandjimbedded in -thedisk..v

L Figure 4 illustrates ashaftsealhavingadouble sealing element, the sealoperatinginfthe sameimanner asV the rabove described'single-elementseal. Theseal shown comprises aY frame 16', al plurality of levers 30',a pair of end members 44' and46f and a pair of annularaseal-Y ingmembers 62 and 64. iThe `sealing membersare positionedV on either sideof a central retainer which may be g in the form of awall or partition65 integral .with the Y ityof levers carried by said support means; atleast one frame. The two sealing-'niemberscooperate with the partitionto form Vradially-extending ,sealing surfaces 66 and 67.V TheY rimportions 24-24 are provided with a plurality ofaxially-extending-sockets andcoil vsprings which act to force Vthesealing members agajnstthe retaining partition. Y Y It `is our intentionto'cover all chang'esQand-modications which do not-depart from the scopeoftheinvention and we do not-wish to be .taken as being limited to theexact embodiments discussedabove .and .intend to claim a novelcentrifugally-compensated shaftY seal as follows: Y

1. A centfugally-compensated annular seal. comprising: cylindricalsupport means affixed to a shaft; a pluralannulai sealing element havingperipheral and radiallyextending Ysealing surfaces, said element beinglactedY on by said levers which pivot lunder-the influence ofcentrifugal force to reduce the'effect of said force on the peripheralsealing lpressure exerted by said elementzon a .Y

cylindrical member disposed concentrically'to said shaft; means carriedby the support means to retainsaid levers and said element in positiononsaid support'means; and means to forceV afradially-extending sealingsurface of said element intoabutmentwithsaid retaining means.

2. A centrifugally-compensated annularseal compris-l ing: a cylindricalseal frame, said frame being aflixedfV to a shaft; a plurality ofaxially-extending"levers,.saidlevers beingV pivotally supportedby saidframe; atrans-Y versely-split resilientv sealing element, said-@elementbeing Vill-'continuous'slidable abutment-With the-insideL-wall.;

of a cylindrialj-inember-disposed concentrically 'to'r said erted bysaid sealing element.

3. For use with concentrically-rotatable shafts, acentrifugallycompensated seal comprising: a plurality ofYaxially-extending, circumferentially-'spaced levers, said levers havingenlarged end portions and elongated neck portions, each neckportionincluding a raised pivot surface and a raised bearing surface, thelatter surface being disposed at the opposite end of said4 neck fromsaid en. larged end; a transversely-split resilient sealing element,said element being in continuous slidable abutment with the inside wallof'an outer shaft; means on said sealing element for engaging thebearing surfaces of said neck portions; a cylindrical frame, said framebeing affixed to an inner shaft and having means Ito pivotally supportsaid levers about said pivot surfaces; retaining means for securing saidlevers and said sealing element on said frame, at least a portion ofwhich retaining means being in abutment with said sealing element, saidlevers being soconstructed and arranged that said engaged lever endswill move radially inward towards the shaft axis in proportion to thespeed of rotation of the innerv shaft to reduce the elfeot ofcentrifugal force on'the peripheral sealingV pressure exerted by saidsealing element on the inside wall of said outer shaft.

4. For use with concentrically-rotatable shafts, lacentrifugally-compensated seal comprising: a cylindrical frame, saidframe being axed to an inner shaft and having axially-spaced edgeportions and a centrally-located rim portion, said rim portion includinga plurality ofV axially-extending holes; a plurality ofaxially-extending levers, said levers being pivotally supported in saidrim holes; an annular transversely-split resilient sealing element, saidelement being in continuous slidable abutment with the inside wall of anouter shaft; means carried by said sealing element for engagement withone end of each of said levers; retainers for securing said levers andsaid sealing element on said frame, said retainers being positioned onsaid frame edge portions with at least one retainer being in continuousslidable abutment with said sealing element, said levers being soconstructed and arranged that said engaged lever ends will move radiallyinward towards the shaft axis in proportion to the speed of rotation ofthe inner shaft to reduce the effect of centrifugal force on theperipheral sealing pressure exerted by said sealing element on theinside wall of said outer shaft.

5. For use with concentrically-rotatable shafts of substantially unequaldiameters, a centrifugally-compensated intershaft seal comprising: acylindrical frame aixed to an inner shaft and having acentrally-'located rimportion; a transversely-cut annular disk, saiddisk being positioned on said frameradjacent said rim portion and havingits f 'periphery in continuous slidable contact with the inside wall ofan outer shaft for sealingf'of the space between said inner and outershafts to `the'passage of uid; a plurality of axially-extending levershaving raised bearing surfaces at one end thereof, said levers beingsupported by the rim portion of said frame; a plurality of apertures inone of the radiall faces of said annular disk for receiving said leverbearing surfaces for relative movement therein; a pair of rings carriedby the frame for securing said levers and said disk on said frame; aplurality of spring members carried by said frame, said spring membersmaintaining the other radial face of said annular disk in continuousabutment with one of said rings, said levers being so constructed andarranged that the bearing surfaces of said levers will move radiallyin-` ward towards the shaft axis in proportion tothe speed of rotationofthe inner shaft to reduce the effect of centrifugal force on theperipheral sealing pressure exerted by said disk on the inside wall ofsaid outer shaft.

6. In combination with conceutrically-rotatable shafts of substantiallyunequal diameters, an intershaft seal comprising: a plurality ofaxially-extending, lever-pins, said pins having an enlarged portion atone end thereof, an

elongated neck portion extending axially from said enlarged end, araised pivot surface positioned centrally of said neck, and a bearingsurface at the other end of said neck from said enlarged end; anannular, transversely-cut disk, the periphery of which is in continuousslidable abutment with the inside wall of the outer shaft for sealing ofthe space between said shaft and the inner shaft to the passage offluid; a plurality of apertures in one of the radial faces of said diskadapted to receive the bearing surfaces of said pins for relativemovement therein; supporting means for said disk and said pins axed tosaidV inner shaft; retaining membersadapted for engagement with saidsupporting means, said retaining members securing said pins and saidannular disk therebetween; a

plurality of spring members carried by said supporting means formaintaining said disk in abutment with one of said retaining members,said seal being so constructed and arranged that the enlarged endportions of said pins will move radially outward under the inuence ofcentrifugal force to pivot the pins and cause said'other pin ends tomove radially inward in proportion to the speed of rotation of the innershaft to reduce the effect of said force on the peripheral sealingpressure exerted by said disk on the inside wall of said outer shaft.

7. A centrifugally-compensated annu-lar seal comprising: a cylindricalseal frame aixed -to a shaft, said frame having a centrally-located,circumferentially-extending partition; a plurality of axially-extendinglevers, said 'levers being pivotally supported by said frame; a pair ofannular sealing elements positioned on said frame on either side of saidpartition, said elements having their peripheries in continuous abutmentwith the inside Wall of a cylindrical member disposed concentrically tosaid shaft; means on each of said sealing elements adapted forengagement with one end of each of said levers; annular means forsecuring said levers and said sealing elements on said frame; and springmembers carried by the frame for maintaining the sealing elements incontinuous abutment with said partition, (said levers being soconstructed and arranged that said engaged lever ends will move radiallyinward towards the shaft axis in proportion to the speed of rotation ofthe shaft-to reduce the effect of centrifugal force on the peripheralsealing pressures exerted by said elements.

No references cited.

